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Comment by CodeIsTheEnd | Hacker News Reader

Directly related to dithering and compression, Return of the Obra Dinn is, to an certain extent, an "unstreamable game".

When this streamer on Twitch tried to play it [1], the quality of his composited webcam would immediately drop as the compression algorithm focused on rendering the high-frequency dithering sections of the screen. As soon as he would aim the camera away from the fancy rendering (to the sky for instance, or the menu), the video quality would immediately improve. Really a fascinating clip.

[1]: https://imgur.com/S191sI0

Here's a thread of someone complaining about it on Reddit:

https://www.reddit.com/r/Twitch/comments/ls06j5/the_unstream...

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The devlog [1] for that game is incredibly interesting, would strongly recommend to anyone interested in game development. If I recall correctly this compression problem almost made him reconsider the whole game - how can your indie game get any momentum if it's unwatchable on youtube/twitch? Luckily for us he persisted. Obra Dinn is one of the most interesting games I've ever played.

[1] https://forums.tigsource.com/index.php?action=profile;u=3073...

I hadn't thought of that, but this is hilarious, and illustrates my point perfectly.

If your compression algorithm isn't aware of the exact dither you're using, the decompressor can't reproduce the dither on the other end using only rules and image data. The compressor needs to encode every single dither pixel as an expensive "Hey decompressor, you're never going to be able to guess this pixel value, so here's the whole thing" residual value.

This is also why old image compression algorithms that were aware of simple dithers (i.e. a handful of fixed grid patterns) could produce small-ish images that looked slightly better than un-dithered, but still kind of bad. But then as soon as you customized the dither to use a more random looking pixel arrangement that looked significantly better, the filesize would explode -- because the compressor was blissfully unaware of the more complicated dither and had no choice but to encode all of the seemingly random pixels directly.

Do you know if they tried the other rendering modes (shaders?) included in the game? From memory there were at least five and some of them looked more suitable for livestreaming.

That’s pretty amazing analysis.

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